Fuller's conception of "Customary Law"
"I shall argue that the phenomenon called "customary law" can best be described as a language of interaction. To interact meaningfully, men require a social setteing in which the moves of the participating players will fall generall within some predictable pattern. To engage in effective social behavior, men need the support of intermeshing anticipations that will let them know what their opposite numbers will do, or that will at least enable them to gauge the general scope of the repertory from which responses to their actions will be drawn." (p.173)
Lon L. Fuller, Human Interaction and the Law, In The Rule of Law, edited by Rbert Paul Wolff, Newyork: Simon and Schuster, 1971, pp. 171-217.